AbbVie (ABBV 0.54%), which was spun out of health care stalwart Abbott Laboratories (ABT 0.29%) at the start of 2013, has beaten the market -- and its former parent company -- by leaps and bounds this year. It reported solid second-quarter results, largely fueled by 16% year-over-year sales growth of its top-selling autoimmune disease drug, Humira, but are there any threats to AbbVie's most important product? In the following video, from The Motley Fool's health-care show Market Checkup, analysts David Williamson and Max Macaluso review the highlights from AbbVie's second-quarter results, discuss the company's dependence on its high-flying blockbuster drug, and explain potential competitive threats to Humira, such as Pfizer's drug Xeljanz.